Question 1

Which of the following statements best describes the law of conservation of electric charge?

Accepted Answer

The total electric charge in an isolated system remains constant during any process.

Question 2

A glass rod is rubbed with silk, and the rod becomes positively charged. What is the best explanation for this observation?

Accepted Answer

Electrons are transferred from the glass rod to the silk, leaving the rod with a net positive charge.

Question 3

Which of the following materials is classified as a semiconductor?

Accepted Answer

Silicon

Question 4

A neutral metal sphere is brought near a negatively charged rod, but they do not touch. What happens to the charges in the sphere?

Accepted Answer

Electrons in the sphere are repelled, causing one side to become positively charged and the other negatively charged.

Question 5

Which equation correctly expresses Coulomb’s Law for the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = k_{el} \frac{q_1$ q_2$}{r^2$}$$

Question 6

If the distance between two point charges is doubled, what happens to the magnitude of the electrostatic force between them?

Accepted Answer

It becomes one-fourth as large.

Question 7

Which of the following is NOT a similarity between Coulomb’s law and Newton’s law of gravitation?

Accepted Answer

In both laws, the force is always one of attraction between the two particles.

Question 8

A charged particle with charge $$q$$ and mass $$m is $$placed in a uniform electric field $$E. $$What is the acceleration $$a of $$the particle?

Accepted Answer

$$a = \frac{qE}{m}$$

Question 9

Which of the following statements about electric field lines is FALSE?

Accepted Answer

Electric field lines can cross each other.

Question 10

A parallel plate capacitor has plates of area $$A$$ and charge $$Q on $$each plate. What is the magnitude of the electric field between the plates?

Accepted Answer

$$E = \frac{Q}{\$$varepsilon_0$$ A}$$

Question 11

Which of the following best explains why you are safe inside a car during a lightning storm?

Accepted Answer

The metallic frame of the car acts as a conductor, ensuring the electric field inside is zero.

Question 12

Which of the following statements about conductors in electrostatic equilibrium is correct?

Accepted Answer

The electric field inside the conductor is zero.

Question 13

A positively charged rod is brought near a neutral insulator. What happens to the insulator?

Accepted Answer

The atoms in the insulator become polarized, creating induced dipoles.

Question 14

Which of the following is the SI unit of electric field?

Accepted Answer

$$\mathrm{N/C}$$

Question 15

A conductor is initially neutral. It is touched by a rod with a net positive charge and then the rod is removed. What is the final state of the conductor?

Accepted Answer

The conductor will have a net positive charge.

Question 16

Which of the following best describes the direction of the electric field at a point in space?

Accepted Answer

The direction of the force on a positive test charge placed at that point.

Question 17

A charged particle is placed in a region where the electric field is directed north. If the particle is positively charged, what is the direction of the force acting on it?

Accepted Answer

North

Question 18

Which of the following is a property of an electric dipole?

Accepted Answer

It consists of equal and opposite charges separated by a distance.

Question 19

Which of the following statements about insulators in external electric fields is correct?

Accepted Answer

The total field inside the insulator is less than the external field but not zero.

Question 20

A positively charged comb is brought near small pieces of paper (insulators). Why are the paper pieces attracted to the comb?

Accepted Answer

The electric field of the comb induces a separation of charges in the paper, creating an attractive force.

Electric Charge, Forces, and Fields: Foundations of Electrostatics

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